Odd-even oscillations in structural and optical properties of gold clusters

Density Functional Theory (DFT) calculations suggests odd-even oscillations in structural, geometrical and optical properties of neutral Au-clusters (n = 2-20). Such odd-even oscillations are understood on the basis of the presence of SOMO in the case of the odd-membered clusters. An analysis of the Mulliken spin-density shows that the negative charges are localized on the edge-atoms on the clusters while the core-atoms are electron deficient. Interestingly, the color of the clusters also shows an odd-even oscillation. A rule similar to the Woodward-Fieser rules is proposed for predicting the average red-shift in visible spectra in these nanoclusters.